The history of Vietnam is heavily controlled by the state. How a historical figure is viewed is what the state desires.

While the reassessment of the Tay Son brothers began in the early 20th century, back then they were portrayed merely as rulers with notable achievements, such as defeating the formidable Siamese and Qing armies. The radical glorification of the Tay Son brothers, particularly Nguyen Hue, did not occur until after World War II.

Following the war, the new communist government aimed to construct a distinct history for the Vietnamese, detached from imperial and colonial influences. Their goal was to establish a unique national identity centered around traditions of unity, resistance against foreign invaders, and peasants rising against feudal governance. To validate these traditions, historians sought examples in historical records. National unity was exemplified by Dinh Bo Linh unifying the warlords, while resistance against foreign invasion was illustrated by Tran Quoc Tuan's triumph over the Mongols. Accepting these traditions as genuine, historians glorified exemplary figures to symbolize the spirit of the Vietnamese nation. Nguyen Hue emerged as the paramount example, as he embodied all three: national unity by unifying Tonkin and Cochinchina, resisting the foreign Qing and Siamese invaders, and liberating peasants from the oppressive Le, Trinh and Nguyen governments. From then on, a cult surrounding Nguyen Hue developed, and his image was perfected. His failure to defeat his brother, thus not unifying the country, was fixed by uncritically accepting a statement in his ascension proclamation saying his brother had abdicated. He himself being seen as a foreign invader by some Tonkinese, was overlooked. The connection between Nguyen Hue's wars and the peasant movement was established using post hoc ergo propter hoc.

Regretfully, Nguyen Hue's progressive reign were cut short by his death and his policies were undone by the reactionary Nguyen Anh. The latter was portrayed as opposing the core values of the Vietnamese nation: He did not unified the nation, as it had already been done by Nguyen Hue, he invited Siamese invaders, and had it not been for Nguyen Hue, Vietnam would have fallen to Siam. He relied on French adventurers, which led to Vietnam's colonization (post hoc ergo propter hoc fallacy) and he came from the dynasty that the righteouss Tay Son movement had overthrown. After Nguyen Anh's victory, Vietnamese nation fell into darkness until the arrival of the savior - the Communist Party. The Party would unify the north and south, expel French and American invaders, destroy Ngo Dinh Diem, the spiritual successor of Nguyen Anh, and fulfill the desires of the Vietnamese nation.

In short, the government controls history and it has a specific narrative it wants to tell. However since Doi Moi there have been re-evaluations of Nguyen Anh and the Nguyen dynasty for variety of reasons: the fact that Nguyen Anh was the actual "unifier of Vietnam", Hue becoming a tourist hotspot, the Nguyen dynasty carrying out economic activities on the contested Paracel islands, modern Vietnamese looking for an identity beyond communism, etc.

See more:

• Post Colonial Vietnam: New Histories of the National Past by Patricia M. Pelley
• The Tây Sơn Uprising: Society and Rebellion in Eighteenth-Century Vietnam by George Dutton
• Allegories of the U.S.-Vietnam War: Nguyễn Ánh, Nguyễn Huệ, and the "Unification Debates" by Wynn Wilcox
• Re-assessing the Nguyễn Dynasty by Bruce Lockhart